The present invention relates to ultrasonics and, more particularly, to the ultrasonic resonant response of components. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).
Ultrasonics has a number of applications to the determination of various material and component characteristics. In one application, the transmission of ultrasonic waves is detected to determine the presence of internal anomalies in a component. In another application, the thickness of a component is determined from the resonant response of a portion of the component located adjacent a transmitter/receiver transducer. These applications generally require transducer access to a flat surface in proximity to a localized volume of the component to be measured. Yet another application involves modal analysis, where the acoustic resonances of a component are excited and the response amplitudes are measured to predict component failure. All these applications depend on the amplitude of a detected response, which, in turn, may depend on the temperature, the exact location of the transducer, acoustic coupling, and other variables.
Resonant ultrasound spectroscopy has been used to determine various properties of solid materials, particularly elastic constants. This application is discussed in U.S. patent application Ser. No. 406,007, now U.S. Pat. No. 4,967,148 Resonant Ultrasound Spectrometer, incorporated herein by reference. The resonant response spectrum of small parallelepiped specimens is determined for use in computing the material elastic constants.
It would be desirable to provide an ultrasonic inspection method that does not require flat surfaces for application of the acoustic wave, that provides reproducible results independent of the location of the transmitter/receive transducers, and is relatively insensitive to temperature, coupling, and other variables that are difficult to control. These problems are addressed by the present invention and a resonant ultrasound spectrographic technique is presented for uniquely characterizing an object.
Accordingly, it is an object of the present invention to provide a characteristic ultrasonic signature of an object that is not dependent on a particular location of ultrasonic transducers.
It is another object of the present invention to provide an ultrasonic inspection method that does not require flat surfaces for the introduction and reception of an acoustic wave.
One other object is to provide an acoustic signature that is relatively insensitive to uncontrolled variables such as temperature and acoustic coupling.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.